Preparation of hard super-hydrophobic films with visible light transmission

Hard super-hydrophobic thin films were prepared combining a phase separation of tetraethyl orthosilicate (TEOS) induced by the addition of an acrylic polymer, and subsequent fluoroalkylsilane (FAS) coating. The microstructure of the films was crater-like, and the structural dimension depended on the degree of the phase separation. The dominant mechanism of the hydrophobicity of the film was changed from Wenzel’s mode to Cassie’s mode with increasing surface roughness. The film obtained by proper composition possessed high transmittance in the visible wavelength range and its hardness was almost at the same level as normal silica-based hard coatings.